氧化铝基复合陶瓷-金属钎焊界面的热应力

Thermal residual stresses near interface brazing aluminia matrix composite to metal

关键词:  复合陶瓷-金属钎焊  界面  残余应力  有限元法

Key words:  ceramic matrix composite-metal brazing  interface  residual stress  finite element method

摘要:

用Ag-Cu-Ti钎料钎焊SiC_w/Al₂O₃复合陶瓷和金属时,陶瓷与钎料发生化学反应,在陶瓷表面形成由TiO、TiC等物相组成的反应层。采用有限元法,对SiC_w/Al₂O₃复合陶瓷/反应层界面的热应力进行了计算。结果表明,复合陶瓷/反应层界面的残余应力变化急剧,最大拉应力位于晶须、基体和反应层交界处;晶须内部及其表面存在较高的双向压应力,Al₂O₃基体主要承受垂直于界面的拉应力;SiC晶须/反应层界面及其附近的反应产物TiC内具有较高的平行于界面的拉应力,当连接界面承受剪力作用时,SiC晶须/反应层界面和TiC处极易破坏。借助TEM和SEM观察了复合陶瓷/反应层界面区的精细结构和剪切断口形貌,并利用计算结果对观察到的现象进行了分析。

Abstract:

The chemical reaction of the composite with the brazing alloy takes place and the reaction layer,composed of TiO,TiC and so on,forms on the composite surface when SiC_w/Al₂O₃ composite is brazed to metals using Ag-Cu-Ti brazing filler alloy.The thermal residual stresses near the composite/reaction layer interface were calculated by finite element method.The results have shown that the residual stresses near the interface change abruptly,and the highest tensile stress appears at the intersection of the whisker,matrix and reaction layer.High compressive stresses develop in the whisker and on its surface,while the Al2O3 matrix is mainly subjected to the tensile stress perpendicular to the interface.The high tensile stress parallel to the interface exists at the whisker/reaction layer interface and in TiC near the interface,at which failure occurs easily when shear force is applied.Microstructure of the interface region and shear fracture surface of the brazed joints are observed by transmission electron microscope and scanning electron microscope,and the phenomena are analyzed from the calculated results.